Safety drill table



Jan. 3, 1933.

Z. WlTKlN SAFETY DRILL TABLE Original Filed Aug. 28. 1929 g'wuentoz Z a ra Wz'T/rz'n $511 5% Patented Jan. 3, 1933 PATENT OFFICE ZARA WITKIN, OF LOS ANGELES, CALIFORNIA SAFETY DRILL TABLE Application filed August 28, 1929, Serial No. 388,936. Renewed May 23, 1932.

This invention relates to deep well drilling, and particularly to the construction of rotary tables by means of which the drill stem is rotated. In this method of drilling it frequently happens that the drill bit encounters dense format-ion while the drill stem is rotating at high speed. This frequently causes twist-offs of the drill stem and is a source of inconvenience, delay, and some- 1 times the cause of protracted fishing operations in the well, or abandonment of the well. This results in delay in the bringing in of wells and represents a considerable financial loss in conducting well drilling operations.

The general object of this invention is to provide a safety rotary drill table having means for preventing the occurrence of such twist-oil's of a drill stem.

A further object of the invention is to provide the rotary drill table with means whereby a limit may be set to the torque that can be impart-ed through the table to the drill stem.

Further objects of the invention will appear hereinafter. V

The invention consists in the novel parts and combinations of parts to be described hereinafter, all of which contribute to produce an efficient safety drill table.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out inthe appended claims.

In the drawing:

Figure 1 is a plan showing a portion of the center of a drill table, the outer portion of the table being broken away, and illustrating an embodiment of my invention.

Figure 2 is a vertical section through the 40 drill table taken about on the line 2-2 of Figure 1.

Figure 3 is a perspective illustrating half of a liner which constitutes a feature of my invention.

In rotary drilling, a rotary table is employed mounted to rotate on a vertical axis coinciding with the vertical axis of the drill stem. This table usually has a square opening in its center in which outside bushings are set, and these outside bushings support inner bushings which have recesses on their adjacent faces that cooperate to form a square opening to engage the Kelly for driving the drill stem. According to my invention 1 provide a construction for the inner bushing which will prevent the drill stem bein subjected to suflicient torque to twist it off? Referring more particularly to the parts, 1 represents the central portion of a drill table which may be of any common construction mounted for rotation on a vertical axis coinciding with thevertical axis of the well. These rotary tables usually have a bevel gear ring mounted at their outer edge which is driven by a pinion on a horizontal shaft.

The table 1 has a central opening 2 which is usually of square form as illustrated, and in this opening2 an outer bushing 3 is mounted consisting of two substantially rectangular sections 3 and 3. The outer bushing has a substantially square opening 4 in which the inner bushing 5 is mounted.

This inner bushing comprises two sections 5 and 5 which are of substantially rectangular form, their lower ends 6 being slightly tapered to fit the tapered opening 7 that is fgrmed in the lower portion of the outer bushmg 3.

According to my invention I construct the inner bushing 5 so that these sections 5 and 5 are formed of two parts, for example, the section'5 is composed of an outer section 8 and an inner section 9. The other inner bushing section is similarly constructed.

The section 8 of each inner bushing is formed on its inner face with a semi-cylindrical bore 10 and when the two sections 5 and 5 come together, these recesses 10 cooperate to form a bore. The inner section 9 of each inner bushing is formed with a semi- 2 iseaeeo tubular neck 11 of proper diameter to fit snugly in the bore 10. These sections 9 are also formed on their adjacent faces with rectangular recesses is that come together to form a square opening to receive the Kelly that is car ied on the drill stem. These sections 9, in other words, cooperate to form a liner which is capable of rotation in the bore 10. The liner is preferably supported by providing a flange 13 at the upper ends of he semi-tubular sleeves or bodies of the sections 9 that form a liner. This flange 13 is received in a counter-bore 1 lformed in the upper face of the outer sections of the inner bushing.

In order to impart the driving torqu to the Kelly 15, (see Figure 2), I provide frangible means that connects the outer sections of the inner bushing to the liner. For this purpose I prefer to provide a plurality of sockets 16 in the flange 18, and these sockets are aligned with corresponding sockets 17'. \V hen these sockets are in alignment with each other, I place frangible pins 18 in them. These pins are preferably formed with square heads, (see Figure l) and have cylindrical bodies that are received in the holes i7 that are drilled through the flange 13 and in the upper side of the shoulder 19 on vhich the flange "ests, (see Figure 2). I prefer to provide at least four of these sockets l6 and 17. This enables me to use a number of pins equal to the number of inches diameter of the pipe. The total cross section of the pins employed of course practically determines the limit of torque which can be imparted from the table to the Kelly. I provide bllfflCiQllt area in these pins to impart about of the amount of torque which would be necessary to twist off the drill. This gives a sufficient margin of safety for all practical purposes.

While 1 have referred to these pins as being frangible, it is to be understood that they are not of easily sheared material be cause a drill stem is capable of resisting a relatively high torsional force before it twists off. I call these pins frangible because they are intended to shear before the drill stem twists of.

In the operation of this rotary table, if the pins shear the outer bushing 3 continues to rotate with the table, although the liner formed of the two sections 9 remains st.- tionary with the Kelly; the tubular body of the liner simply rotates freely in the bore 10.

In order to insure that the liner will rotate freely in the outer sections of the inner bushing and to prevent any possibility of the vertical faces 20 on the flanges lll'ef; fering with the free rotation, I round their lower edges as indicated by the shading in ure 3. This prevents forming a sharp edge at the point 20 which might come in contact with an upwardly projecting edge on one of the meeeting faces 21 of the outer sections 8 of the inner bushing. I also provide circumferential ribs 21 on the under side of the flange 13 to reduce the area of contact of the flange with the supporting shoulder 19. This reduces the friction developed between these parts after the pins have sheared.

hat I claim is:

1. In a safety rotary drill table to prevent twist-oil's of a drill stem in drilling a deep well, the combination of a pair of inside bushings supported by, and at the center of the table said inside bushings having means formed between their meeting faces, for rotating the drill stem, each inside bushing consisting of an outer section of substantially rectangular form to fit into the opening in the table and a sectional liner having a semi-cylindrical neck with a flange at its upper end supported on the upper end of the outer section, said outer sections forming a cylindrical bore between them receiving and centering the said necks of the inner sections and frangible means passing through the flange and seating in the outer section of the inner bushing, said frangible means operating to shear and permit rotation of the liner in the outer sections of the inner bushing when a predetermined torque is being imparted to the drill stem through the rotary table.

2. In a safety rotary drill table to prevent twist-offs of a drill stein in drilling deep well, the combination of a pair of inside bushings supported by, and at the center the table, having an angular opening formed between their meeting faces, for rotating the drill stem, each insit c bushing consisting of an outer section of substantially rectangular form to fit into the opening in the table and a sectional liner having a semi-cylindrical neck with a flange at its upper end supported on the upper end of the outer section, said outer sections forming a cylindrical bore. between them receiving and centering the said necks of the inner sections and a plurality of frangible pins mounted in the flange and passing through the same into the outer section of the inner bushing, said pins operating to shear and permit rotation of the liner in the inner section of the inner bushing when a predetermined torque is being imparted through the rotary table.

3. In a safety drill table to prevent twistoifs of a drill stem in drilling a deep well, the combination of a pair of inside bushings supported by, and at the center of the table, having means formed between their meeting faces, for rotating the drill stem, each inside bushing consisting of an outer section of substantially rectan ular form having a bore on its inner side with a liner fitting snugly into, and held centered by, said bore, and frangible means connecting the outer section of the inner bushing with the liner operating to shear and permit rotation of the liner when a predetermined torque is being imparted to the drill stem through the rotary table.

a. In a safety rotary drill table to prevent twist-off of a drill stem in drilling a deep well, the combination of a pair of inside bushings supported by, and at the center of the table, having an angular opening formed between their meeting faces, for rotating the drill stem, said inside bushings comprising outer sections having semi-cylindrical recesses on their adjacent faces meeting together to form a bore, and having two inner sections meeting together to form a liner with a cylindrical neck received in, and held centered by, the said bore, said liner having a flange at its upper end with a plurality of sockets therein, the outer sections of the inside bushings having sockets to align with the first named sockets, and removable frangible pins received in said sockets for imparting torque from the table to the drill stem, said pins operating to shear and permit rotation of the liner in the outer sections of the inner bushing when a predetermined torque is being imparted to the drill stem.

5. In a safety rotary drill table to prevent twist-offs of a drill stem in drilling a deep well, the combination of a pair of inside bushings supported by, and at the center of the table, having an angular opening formed between their meeting faces, for rotating the drill stem, each inside bushing consisting of an outer section of substantially rectangular form to fit into the opening in the table and a sectional liner having a semi-cylindrical neck with a flange at its upper end supported on the upper end of the outer section, said outer sections forming a cylindrical bore between them receiving and centering the said necks of the inner sections and frangible means passing through the flange and seating in the outer section of the inner bushing, said frangible means operating to shear and permit r0- tation of the liner in the outer sections of the inner bushing when a predetermined torque the inner sections, and frangible means pass-- ing through the flange and seating in the outer section of the inner bushing, said frangible Signed at Los Angeles, California, this 7 th day of August 1929.

ZARA WITKIN.

is being imparted to the drill stem through the rotary table, said flange having means on its under face to enable the same to rotate freely in the outer sections of the inside bushings if the frangible means should become sheared.

6. In a safety rotary drill table to prevent twist-offs of a. drill stem in drilling a deep well, the combination of a pair of outside bushings supported by the table, a pair of inside bushings supported in the outside bushings at the center of the table, said inside bushings having means formed between their meeting faces for rotating the drill stem, each inside bushing consisting of an outer section of substantially rectangular form to fit into the opening in the outer bushings, and a sectional liner having a semi-cylindrical neck with a flange at its upper end supported on the upper end of the outer section, said outer sections forming a cylindrical bore between them receiving and centering the said necks of 

